Serum estradiol associates with blood hemoglobin in elderly men: the MrOS Sweden study.

CONTEXT Blood hemoglobin (Hb) declines with age in healthy elderly men, in whom decreasing T has been regarded as part of normal aging. However, the association between Hb and serum estradiol is incompletely known. OBJECTIVE To determine whether estradiol is associated with anemia/Hb and established determinants of Hb in elderly men without prostate cancer. DESIGN, SETTING, AND PARTICIPANTS The MrOS (Osteoporotic Fractures in Men) is a population-based study (n = 918; median age, 75.3 y; range, 70-81 y). MAIN OUTCOME MEASURES We evaluated total estradiol in relation to Hb and adjusted for potential confounders (ie, age, body mass index [BMI], erythropoietin [EPO], total T, cystatin C, and iron and B-vitamin status). RESULTS Estradiol correlated negatively with age (r = -0.14; P < .001). Hb correlated (age adjusted) positively with estradiol (r = 0.21; P < .001) and T (r = 0.10; P < .01). Independent predictors for Hb in multivariate analyses were estradiol, EPO, BMI, transferrin saturation, cystatin C, and free T4, but not T. After exclusion of subjects with Hb <130 g/L and/or T < 8 nmol/L (n = 99), the correlation between Hb and T was no longer significant, whereas the associations between Hb and estradiol remained. After adjusting for age, BMI, and EPO, men with lower estradiol levels were more likely to have Hb in the lowest quartile of values (odds ratio per SD decrease in estradiol = 1.61 [95% confidence interval, 1.34-1.93]). Anemic subjects (Hb < 130 g/L) had lower mean estradiol than nonanemic subjects (67.4 vs 79.4 pmol/L; P < .001). CONCLUSIONS Estradiol correlated positively and independently with Hb. Decreased estradiol might partly explain the age-related Hb decline observed in healthy elderly men.